Avoid polluting user home directory with .ansibullbot

[ssbarnea]

.ansibullbot folder is a cache folder so it should be stored in XDG cache location, ~/.cache and avoid polluting user home directory.

If needed, please consult https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

[mkrizek]

FWIW note that --cachedir is how you can configure the path where cache is stored, it defaults to '~/.ansibullbot/cache.

[ssbarnea]

We should update it to respect the spec, likely to ~/.cache/ansibullbot. I do know that ansible-core is also misbehaving but other tools that we have already ensures they follow the XDG spec (navigator, linter, molecule) and I will not be surprised to also see core doing the same.

The correct implementation looks like https://github.com/ansible-community/ansible-lint/blob/34a27984616e1872a53297af6a7a4ea2b672c4f8/src/ansiblelint/__main__.py#L110-L112